1. Technical Field
This invention relates generally to pistons for internal combustion engines, and particularly those that are made in one piece and to their methods of manufacture.
2. Related Art
It is known in the art to manufacture pistons for internal combustion engines by fabricating a piston blank (by casting, forging, machining, powder metal techniques, or combinations of these operations) and to form in such pistons at least one cooling gallery that is either closed and which may contain a heat-extracting material, such as sodium, or which gallery is at least partially open to receive a flow of cooling oil for cooling regions of the piston adjacent the galley.
One technique for forming the gallery in such pistons is to form an initially open channel in the piston and then to displace, by forging or rolling techniques, a flange of the piston radially outwardly against an outermost surface of the piston body to enclose the gallery, where the resulting joint, located away from a combustion bowl rim of the piston, may be closed by soldering, brazing or welding. Such a technique is generally shown in prior references DE 1103698, DE 1210302, DE 102005021428, US 2009/0241769, US 2008/0273936, U.S. Pat. No. 7,104,183, U.S. Pat. No. 7,421,782, and U.S. Pat. No. 7,761,987.
For some engine applications, such as high performance engines and diesel engines, the piston is subjected to extreme temperature cycles and highly corrosive and erosive gases. In these engines, the combustion bowl region, and particularly an upper rim region of the combustion bowl, is particularly subjected to extreme temperature, pressure, stress and highly corrosive and erosive gases. Accordingly, the combustion bowl rim region is typically considered a likely region of degradation in use.
A piston constructed in accordance with this invention provides a closed, or substantially closed cooling gallery with a combustion bowl having a combustion bowl rim region that is able to withstand the extreme temperature, pressure, stress and highly corrosive and erosive gases in modern high performance and diesel engines, thereby providing the piston with and increased useful operating life.